1. Technical Field of the Invention
The present invention relates to the air interface between a mobile station and a base station, and more particularly, to a method for increasing the uplink bandwidth from a mobile station to a base station over a dedicated control channel.
2. Description of Related Art
As the use of wireless communication services has increased over the past decade, the need for transmitting even more data over a wireless communications link has become necessary. This need has been further increased by the development of a variety of wireless communication services enabling a user to not only have voice communications over a communications link but also to transfer data. The major problem for voice and data transfers over the communications link is caused by bandwidth limitations. The available bandwidth limits the amount of information that can be transmitted over the air interface. Thus, any means for increasing the bandwidth provides a system with the ability to transfer more information and to provide more dynamic voice and data communication services.
There is currently ongoing work in the area of data transfers between mobile stations and base stations. The majority of the work in this area concentrates on increasing the bandwidth of the MS/BS link to enable the transfer of data over a shorter time period. One of the present solutions to this problem involves concatenating individual R-DATA messages in order to exceed the 255 byte limit which is presently imposed by layer 2 of the IS-136 protocol. Other schemes use various channel types in an attempt to increase transmission bandwidth. In some of the schemes, a mobile station will receive a page while camping on a digital control channel (DCCH). The mobile station then moves to a dedicated data channel (DDCH) to send or receive necessary data before returning to the DCCH. This is a reasonable solution when large amounts of data must be transferred. However, when smaller amounts of data must be transferred, for example, during e-mail or web browsing activities, it would be desirable to transfer the data without leaving the DCCH.
Presently, the base station provides a much greater bandwidth on the DCCH when transferring data to the mobile station than when it is receiving data from the mobile station. This is due to the fact that the base station may utilize every downlink frame when transferring data to a mobile station, but the mobile station may only use every sixth uplink frame to transfer data back to the base station. Thus, some method enabling a mobile station to remain upon the dedicated control channel, yet transfer data at a higher bandwidth, would be greatly desirable.
The present invention overcomes the foregoing and other problems with a method for transmitting messages over an air interface between a mobile station and base station having an increased bandwidth. The method initially involves the step of seizing multiple random access channels on a dedicated control channel existing between a mobile station and a base station. A single message may then be transmitted over each of the seized random access channels on a frame-by-frame basis.
The transmission procedure involves monitoring each of the seized random access channels for a shared channel feedback flag indicating that a message frame may be transmitted from the mobile station to the base station on the random access channel. The message frames are transmitted to the base station upon receipt of the indication. Transmissions on the different random access channels will each occur during different frame periods such that no two random access channel frame transmissions overlap each other. Upon transmission of a message frame on a random access channel, the channel is again monitored for the shared channel feedback flag for an indication that the transmitted message frame has been received by the base station. Each random access channel transmission of a message frame will occur approximately four frames after receipt of an indication that a random access channel is available for transmission, and the confirmation of receipt of the transmission frame by the base station is received approximately two frames after transmission of a message frame from the mobile station.